Larry wrote:

Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last summer
I noticed that "on occasion" that boat would seem to "thump" after putting
it in gear. If I stayed at low RPM while leaving the boat ramp, it would
"thump" every few seconds. I couldn't really tell where the thump was
coming from. As soon as I gave it some speed, it worked fine.

I've had it out three times this year so far and today, the thumping was
especially bad. An almost continuous thump at low RPM's, and even some at
middle RPM's. When I have it full open, it seems to be working just fine.

Anybody ever had this, or heard of it, or have any idea what it might be? I
know you can't diagnose over the net, but maybe the symptoms sound familiar.

Thanks!



U-joints.

Rob

"trainfan1" wrote in message
et...
Larry wrote:

Hi:

I bought a 19 foot seasprite boat last summer. It is a 1986. Last
summer
I noticed that "on occasion" that boat would seem to "thump" after
putting
it in gear. If I stayed at low RPM while leaving the boat ramp, it
would
"thump" every few seconds. I couldn't really tell where the thump was
coming from. As soon as I gave it some speed, it worked fine.

I've had it out three times this year so far and today, the thumping was
especially bad. An almost continuous thump at low RPM's, and even some
at
middle RPM's. When I have it full open, it seems to be working just
fine.

Anybody ever had this, or heard of it, or have any idea what it might
be? I
know you can't diagnose over the net, but maybe the symptoms sound
familiar.

Thanks!



U-joints.

U-joints "thump" ? What was the "rate" of the thump? And what is the RPM?
I would think the term used would be more like "vibration" - "thump" implies
that its not following the rate of the turning drive shaft.





Rob

U-joints "thump" ? What was the "rate" of the thump? And what is the RPM?
I would think the term used would be more like "vibration" - "thump" implies
that its not following the rate of the turning drive shaft.

For me it was a resounding "THUMP" every few seconds, at about 1000-2000 RPM,
went up to 3500 it went away; went back down; didn't happen again.


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"Josh Assing" wrote in message
...
U-joints "thump" ? What was the "rate" of the thump? And what is the
RPM?
I would think the term used would be more like "vibration" - "thump"
implies
that its not following the rate of the turning drive shaft.

For me it was a resounding "THUMP" every few seconds, at about 1000-2000
RPM,
went up to 3500 it went away; went back down; didn't happen again.

A fricking "U" joint did this?.... 'who knew'.
Dang, learn something new every day. I
don't unserstand the mechanics behind that
unless it causes some sort of binding or something ?




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"Mr Wizzard" wrote in message
. ..


A fricking "U" joint did this?.... 'who knew'.
Dang, learn something new every day. I
don't unserstand the mechanics behind that

Wait!, you;re not the one suggesting U-joints,
you're the original problem poster. So yeah..
Every "few seconds" isn't U-joints, I just don't
buy that. I'm thinking engine alignment, binding,
coupler, dog-clutch coming disengaged, or
something like that. So tell me, does it sould
the same as the "clunk" (or thump as you say)
you get when putting it in gear? When was the
last time the shifter cable on your Coba replaced?
The 89-ish Cobra's shifter mechanism gets very
"vague" with old/stretched shifter cables. Also,
and so you know, this is a "shift lever" retrofit,
or upgrade that OMC had for that year. (this
device is inside the lower unit.






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the same as the "clunk" (or thump as you say)
you get when putting it in gear? When was the

no; it goes in and out of gear w/o an issue -- it's very crisp and prompt.

last time the shifter cable on your Coba replaced?
The 89-ish Cobra's shifter mechanism gets very
"vague" with old/stretched shifter cables. Also,
and so you know, this is a "shift lever" retrofit,
or upgrade that OMC had for that year. (this
device is inside the lower unit.

I'm going with original - the PO had a lot of notes about what was done; and I
don't see any retrofit (this is a 90; so that counts as 89ish)

-josh


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